Mine was the opposite. I got the car back with all new plugs, and when they delivered it to me, it was misfiring badly. THey had to go back and re-code the injectors, and give me the car the following day.

When I got it back, it was fine, but the stumble came back on over the next couple tanks of gas.

Seems like most people are getting this after a plug change. I just had all my plugs swapped again, and that didn't solve the issue, so it's not like they put bad plugs in.

I think it's injectors, as I still have 2 of the old ones that haven't been replaced per the BMWNA bulletin, but lots of people have had all the injectors replaced, have hte new HPFP, new coilpacks, and new plugs, and still have the issue.

Makes me yearn for hte days of the old diagnostic machines, where you connected wires to all the plugs, and various other parts of the car. Obviously systems are quite a bit more complicated now, but the fact that it's not throwing a code shouldn't be exhaustive in determining that nothing is wrong. However rudimentary, I feel like mechanics were better equipped to diagnose a problem with one of these. Perhaps I'm just getting old.

I have this same problem. When I start the car, it rumbles a bit and you can feel it through the shifter, etc. I just had my spark plugs done maybe a month ago, and do not remember it doing this before. I have had the procede out since my spark plug job, and also have the exhaust plug disconnected. I dont think its misfiring as no check engine light comes on. It's just a little rough at idle. Today, I went to the stores, and came home car is warmed up, and idled it in the garage. After a moment, it stumbled at 600rpm, then rose to 700rpm and stayed there. I shut it off after a minute like that...no stumbles at 700rpm. I wonder what the problem is.

^ Thats the same issue. Interesting the tunes seem to not be having an effect, which means if it is a DME issue, its not in any tables or signals being manipulated by the tuners.

Had the the remaining two old injectors replaced, and will be picking up the car tomorrow. Hopefully that puts my misfire adventuresbehind me, and maybe it'll be the silver bullet on the stumble.

Crossing fingers...

One thing to note, I dont thnk the fact that you dont have a CEL is exhaustive on misfires. I'm pretty positive it takes a repeated and severe misfire for this car to throw a code. My car was definitely having less severe misfires and running poorly, and wasn't throwing a code. Sometimes I could provoke the code with hard driving, but then I could shut off the car, start it back up, and the light would be off, but t'd still be running like shit.

Finally have my misfire woes resolved. Despite no CEL and multiple tries to give me the car back with "the problem solved" I had the Service Manager sit in my car and feel it for himself. They tried one more time to give it back, and I literally drove it out the driveway, and right back into the service area.

They finally aquiesced, and replaced the two remaining old injectors. Occam's Razor.

Still have the stumbling idle / hunting RPMs, but at this point, I'm just glad to have my car back.

It's frustrating that the engine is clearly misfiring and yet no codes are stored. I'm sure it's like you say where only severe, sustained misfiring is enough to trigger a code.

What I'd like to know is whether or not misfires are logged in the ECU despite not triggering a CEL or storing a code. I'd think this could at least point us in the right direction or maybe narrow down a particular cylinder.

Has anyone ever tried running Techron or some other fuel injector cleaner just to see if it makes a difference?

It's frustrating that the engine is clearly misfiring and yet no codes are stored. I'm sure it's like you say where only severe, sustained misfiring is enough to trigger a code.

What I'd like to know is whether or not misfires are logged in the ECU despite not triggering a CEL or storing a code. I'd think this could at least point us in the right direction or maybe narrow down a particular cylinder.

Has anyone ever tried running Techron or some other fuel injector cleaner just to see if it makes a difference?

i tried the Techron cleaner 12oz bottle on a full tank, it didnt really make a difference.

I replaced my plugs with OEM ones from the dealer, i just dont understand why plugs would trigger this, i replaced them at 54k miles.

Just to give you guys an update on my situation, it has been 7k miles since I changed my spark plugs, and I don't have as many blips as I initially had. I still keep the A/C on all the time to keep the rpm high, because it tends to do it less what way. It is annoying, but as long as I don't have misfires under load, I can live with it.

What I'd like to know is whether or not misfires are logged in the ECU despite not triggering a CEL or storing a code. I'd think this could at least point us in the right direction or maybe narrow down a particular cylinder.

I don't think they are.

Quote:

Originally Posted by andy92782

Has anyone ever tried running Techron or some other fuel injector cleaner just to see if it makes a difference?

I have the same problem before I replaced the plugs and after. I read somewhere that when they took the car to the dealer they just increased the idle higher than 600 rpm and it fix the problem no more hiccups!! Haven't tried yet waiting to read more info...

Well add me to the list as well. I did the plugs at 68k and now have just shy of 76k. 2/07 build date. Pulls fine and data logs look fine, but the idle is junk. (subtle, but sometimes more noticeable than usual)